Stress Evolution And Deformation Mechanism Of Floor Under High Abutment Pressure In Roadway Driving Along Filling Body

Aiming at the problem of stress evolution and deformation mechanism of floor under high abutment pressure of roadway driving along backfill,this paper systematically studies the evolution process of floor abutment pressure during the whole process of roadway driving along backfill by means of theoretical analysis and numerical simulation.It reveals the mechanism of roadway floor heave under high abutment pressure of roadway driving along backfill,and explores the mechanism of roadway floor heave under high abutment pressure of roadway driving along backfill.Influencing factors of floor stability under high abutment pressure of driving roadway and its action law are discussed.Meanwhile,Countermeasures of controlling floor heave are put forward.The main conclusions are as follows:(1)According to the key strata theory of strata controlling and the law of overlying strata activity,the mechanical model of roadway floor along backfill is established,and the mechanics analysis of roadway floor along filling body is carried out.(2)Through numerical simulation,the influence of burial depth,lateral pressure coefficient,thickness of surrounding rock,lithology of surrounding rock,strength of backfill and location of main roof breakage on floor heave of roadway driving along backfill are discussed.It is found that the influence of burial depth on floor heave of roadway driving along backfill is most intuitive,and the volume of floor heave increases sharply with the increasing of burial depth;When the basic roof is broken at the upper part of the filling body,the bottom heave is the largest.(3)The evolution process of abutment pressure and the law of floor deformation in the whole process of roadway excavation along backfill are discussed by numerical simulation.It is found that in the process of "primary excavation",the abutment pressure acting on the floor beneath the two sides of the roadway along the filling body appears asymmetric distribution;in the process of "primary mining",two peak abutment pressure appears on the floor,and the abutment pressure of the floor beneath the solid coal is slightly higher than that under the filling body.In the process of "secondary roadway excavation",the peak value of abutment pressure acting on the bottom of backfill body is slightly higher than that of the bottom of entity coal body.At the same time,it is affected by pressure relief and high abutment pressure,and obvious floor heave is produced along the backfill body roadway excavation;In the process of "secondary mining",under the action of superposition of abutment pressure,secondary deformation of surrounding rock of roadway driving along filling body is caused,and the floor heave of roadway driving along filling body isfurther increased.The floor heave reaches its maximum when the working face is 5 meters ahead,and decreases with the distance from the working face.(4)Comprehensive analysis shows that the roadway floor heave along backfill mainly consists of shear slip at the corner of floor and tensile deformation in the middle of floor.Therefore,two kinds of floor heave control measures are put forward to reinforce the floor and relieve the pressure of the floor.It is found that the tensile deformation in the middle of the floor is the main factor affecting the floor heave along the backfill,and the shear slip at the corner of the floor is the secondary factor.Therefore,reinforcement of roadway floor and slope angle can effectively control the deformation of roadway floor along backfill;pressure relief trough can provide effective deformation space for roadway floor,and the floor heave decreases with the increase of depth of pressure relief trough.